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package java.util.logging;

import java.io.*;

/**
 * Stream based logging <tt>Handler</tt>.
 * <p>
 * This is primarily intended as a base class or support class to
 * be used in implementing other logging <tt>Handlers</tt>.
 * <p>
 * <tt>LogRecords</tt> are published to a given <tt>java.io.OutputStream</tt>.
 * <p>
 * <b>Configuration:</b>
 * By default each <tt>StreamHandler</tt> is initialized using the following
 * <tt>LogManager</tt> configuration properties where <tt>&lt;handler-name&gt;</tt>
 * refers to the fully-qualified class name of the handler.
 * If properties are not defined
 * (or have invalid values) then the specified default values are used.
 * <ul>
 * <li>   &lt;handler-name&gt;.level
 * specifies the default level for the <tt>Handler</tt>
 * (defaults to <tt>Level.INFO</tt>). </li>
 * <li>   &lt;handler-name&gt;.filter
 * specifies the name of a <tt>Filter</tt> class to use
 * (defaults to no <tt>Filter</tt>). </li>
 * <li>   &lt;handler-name&gt;.formatter
 * specifies the name of a <tt>Formatter</tt> class to use
 * (defaults to <tt>java.util.logging.SimpleFormatter</tt>). </li>
 * <li>   &lt;handler-name&gt;.encoding
 * the name of the character set encoding to use (defaults to
 * the default platform encoding). </li>
 * </ul>
 * <p>
 * For example, the properties for {@code StreamHandler} would be:
 * <ul>
 * <li>   java.util.logging.StreamHandler.level=INFO </li>
 * <li>   java.util.logging.StreamHandler.formatter=java.util.logging.SimpleFormatter </li>
 * </ul>
 * <p>
 * For a custom handler, e.g. com.foo.MyHandler, the properties would be:
 * <ul>
 * <li>   com.foo.MyHandler.level=INFO </li>
 * <li>   com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li>
 * </ul>
 * <p>
 *
 * @since 1.4
 */

public class StreamHandler extends Handler {

  private OutputStream output;
  private boolean doneHeader;
  private volatile Writer writer;

  // Private method to configure a StreamHandler from LogManager
  // properties and/or default values as specified in the class
  // javadoc.
  private void configure() {
    LogManager manager = LogManager.getLogManager();
    String cname = getClass().getName();

    setLevel(manager.getLevelProperty(cname + ".level", Level.INFO));
    setFilter(manager.getFilterProperty(cname + ".filter", null));
    setFormatter(manager.getFormatterProperty(cname + ".formatter", new SimpleFormatter()));
    try {
      setEncoding(manager.getStringProperty(cname + ".encoding", null));
    } catch (Exception ex) {
      try {
        setEncoding(null);
      } catch (Exception ex2) {
        // doing a setEncoding with null should always work.
        // assert false;
      }
    }
  }

  /**
   * Create a <tt>StreamHandler</tt>, with no current output stream.
   */
  public StreamHandler() {
    sealed = false;
    configure();
    sealed = true;
  }

  /**
   * Create a <tt>StreamHandler</tt> with a given <tt>Formatter</tt>
   * and output stream.
   * <p>
   *
   * @param out the target output stream
   * @param formatter Formatter to be used to format output
   */
  public StreamHandler(OutputStream out, Formatter formatter) {
    sealed = false;
    configure();
    setFormatter(formatter);
    setOutputStream(out);
    sealed = true;
  }

  /**
   * Change the output stream.
   * <P>
   * If there is a current output stream then the <tt>Formatter</tt>'s
   * tail string is written and the stream is flushed and closed.
   * Then the output stream is replaced with the new output stream.
   *
   * @param out New output stream.  May not be null.
   * @throws SecurityException if a security manager exists and if the caller does not have
   * <tt>LoggingPermission("control")</tt>.
   */
  protected synchronized void setOutputStream(OutputStream out) throws SecurityException {
    if (out == null) {
      throw new NullPointerException();
    }
    flushAndClose();
    output = out;
    doneHeader = false;
    String encoding = getEncoding();
    if (encoding == null) {
      writer = new OutputStreamWriter(output);
    } else {
      try {
        writer = new OutputStreamWriter(output, encoding);
      } catch (UnsupportedEncodingException ex) {
        // This shouldn't happen.  The setEncoding method
        // should have validated that the encoding is OK.
        throw new Error("Unexpected exception " + ex);
      }
    }
  }

  /**
   * Set (or change) the character encoding used by this <tt>Handler</tt>.
   * <p>
   * The encoding should be set before any <tt>LogRecords</tt> are written
   * to the <tt>Handler</tt>.
   *
   * @param encoding The name of a supported character encoding. May be null, to indicate the
   * default platform encoding.
   * @throws SecurityException if a security manager exists and if the caller does not have
   * <tt>LoggingPermission("control")</tt>.
   * @throws UnsupportedEncodingException if the named encoding is not supported.
   */
  @Override
  public synchronized void setEncoding(String encoding)
      throws SecurityException, java.io.UnsupportedEncodingException {
    super.setEncoding(encoding);
    if (output == null) {
      return;
    }
    // Replace the current writer with a writer for the new encoding.
    flush();
    if (encoding == null) {
      writer = new OutputStreamWriter(output);
    } else {
      writer = new OutputStreamWriter(output, encoding);
    }
  }

  /**
   * Format and publish a <tt>LogRecord</tt>.
   * <p>
   * The <tt>StreamHandler</tt> first checks if there is an <tt>OutputStream</tt>
   * and if the given <tt>LogRecord</tt> has at least the required log level.
   * If not it silently returns.  If so, it calls any associated
   * <tt>Filter</tt> to check if the record should be published.  If so,
   * it calls its <tt>Formatter</tt> to format the record and then writes
   * the result to the current output stream.
   * <p>
   * If this is the first <tt>LogRecord</tt> to be written to a given
   * <tt>OutputStream</tt>, the <tt>Formatter</tt>'s "head" string is
   * written to the stream before the <tt>LogRecord</tt> is written.
   *
   * @param record description of the log event. A null record is silently ignored and is not
   * published
   */
  @Override
  public synchronized void publish(LogRecord record) {
    if (!isLoggable(record)) {
      return;
    }
    String msg;
    try {
      msg = getFormatter().format(record);
    } catch (Exception ex) {
      // We don't want to throw an exception here, but we
      // report the exception to any registered ErrorManager.
      reportError(null, ex, ErrorManager.FORMAT_FAILURE);
      return;
    }

    try {
      if (!doneHeader) {
        writer.write(getFormatter().getHead(this));
        doneHeader = true;
      }
      writer.write(msg);
    } catch (Exception ex) {
      // We don't want to throw an exception here, but we
      // report the exception to any registered ErrorManager.
      reportError(null, ex, ErrorManager.WRITE_FAILURE);
    }
  }


  /**
   * Check if this <tt>Handler</tt> would actually log a given <tt>LogRecord</tt>.
   * <p>
   * This method checks if the <tt>LogRecord</tt> has an appropriate level and
   * whether it satisfies any <tt>Filter</tt>.  It will also return false if
   * no output stream has been assigned yet or the LogRecord is null.
   * <p>
   *
   * @param record a <tt>LogRecord</tt>
   * @return true if the <tt>LogRecord</tt> would be logged.
   */
  @Override
  public boolean isLoggable(LogRecord record) {
    if (writer == null || record == null) {
      return false;
    }
    return super.isLoggable(record);
  }

  /**
   * Flush any buffered messages.
   */
  @Override
  public synchronized void flush() {
    if (writer != null) {
      try {
        writer.flush();
      } catch (Exception ex) {
        // We don't want to throw an exception here, but we
        // report the exception to any registered ErrorManager.
        reportError(null, ex, ErrorManager.FLUSH_FAILURE);
      }
    }
  }

  private synchronized void flushAndClose() throws SecurityException {
    checkPermission();
    if (writer != null) {
      try {
        if (!doneHeader) {
          writer.write(getFormatter().getHead(this));
          doneHeader = true;
        }
        writer.write(getFormatter().getTail(this));
        writer.flush();
        writer.close();
      } catch (Exception ex) {
        // We don't want to throw an exception here, but we
        // report the exception to any registered ErrorManager.
        reportError(null, ex, ErrorManager.CLOSE_FAILURE);
      }
      writer = null;
      output = null;
    }
  }

  /**
   * Close the current output stream.
   * <p>
   * The <tt>Formatter</tt>'s "tail" string is written to the stream before it
   * is closed.  In addition, if the <tt>Formatter</tt>'s "head" string has not
   * yet been written to the stream, it will be written before the
   * "tail" string.
   *
   * @throws SecurityException if a security manager exists and if the caller does not have
   * LoggingPermission("control").
   */
  @Override
  public synchronized void close() throws SecurityException {
    flushAndClose();
  }
}
